With our ethnically diverse longitudinal twin study, we aim to understand the genetic and environmental mechanisms by which the infant, toddler and childhood family sociocultural environments impact day-to-day associations between quality of sleep and health-related behaviors. Also, we elucidate mechanisms accounting for the longitudinal association between dynamic sleep processes and physical health and academic functioning in middle childhood. Without the use of a genetically-informed design, environmental causation cannot be inferred because quality of sleep is heritable, components of the family environment are also heritable through gene-environment correlation, and thus their covariation may be genetically or environmentally mediated. Salient aspects of the environment include a) family values and stressors (including culture-specific stressors), b) home stability and chaos and c) responsive and negative parenting. Specifically, under Aim 1 we model within person dynamic sleep and health behavioral processes in middle childhood, and the role of the sociocultural environment in moderating these processes. Under Aim 2, we predict physical health and academic functioning from children's average and dynamic sleep and health behavioral processes two years earlier. We also examine the extent to which these dynamic processes mediate the associations between the sociocultural environment and later physical health and academic functioning. With Aim 3, we use the twin method to document genetic and environmental contributions to multiple components of children's sleep, health and academic outcomes. Under Aim 4, we use the twin method to determine the extent to which the measured sociocultural environment moderates the heritability of sleep and health behaviors. This study would be the first to use a genetically-informative dynamic daily approach to understand sociocultural environment-sleep relations. The proposed study forms a new collaboration of a young team of investigators with complementary expertise. The project is notable for its developmental cultural and genetic approach that uncovers gene-environment interplay, extensive assessment of the sociocultural environment during a sensitive period for brain development, establishment of a circadian rhythm, and formation of bedtime routines and habits. Under a resilience framework, we study protective as well as risk processes, as protective environments such as sensitive parenting and bedtime routines likely offset genetic or environmental risk for sleep problems. Combining these design features exponentially increases the scientific contribution by elucidating processes that support preventive intervention efforts.